Lid for a tank of a fluid system, such as a cooling water circuit of an automotive vehicle

ABSTRACT

The lid for a tank of a fluid system such as a cooling water circuit of an automotive vehicle is characterized in that the lid is composed of an inner lid member which can be screwed to the neck of the tank, and of an outer lid member which covers the inner lid member in the manner of a bell or mushroom, and that a coupling means is formed between the inner lid member and the outer lid member, the coupling means containing a medium which below a predetermined temperature or a predetermined temperature range shows such a consistency that the medium establishes a non-rotational connection between the outer lid member and the inner lid member while the medium above the predetermined temperature or the predetermined temperature range assumes such a consistency that the outer lid member is rotatable relative to the inner lid member. It is thereby ensured that endangerment of persons by hot liquid or coolant steam squirting out therefrom is reliably prevented.

The present invention relates to a lid for a tank of a fluid system suchas a cooling water circuit of an automotive vehicle, the lid beingpreferably adapted to be screwed to a neck of the tank. The presentinvention is also applicable to lids of tanks of other fluid systems,such as cooling water circuits of a combined heat and power machine oranother technical apparatus, wherein the fluid is heated to a hightemperature, so that it may be dangerous to open a service or inspectionlid of the tank.

When the lid of an expansion tank of an automotive vehicle is openedafter the engine of the automotive vehicle has been running for sometime and the cooling water has been heated thereby, persons might getseriously injured by hot coolant or coolant steam squirting outtherefrom. To reduce this risk, it is known to lock the lid by means ofa locking nose so that coolant steam can escape in a first openingposition of the lid before the lid is fully opened. However, if the riskis not known, the lid may be rapidly opened to such an extent thatscalds may occur after all.

It is the object of the present invention to further develop a lid for atank of a fluid system of the above-considered type in such a mannerthat endangerment of persons by a hot coolant or coolant steam squirtingout therefrom is reliably prevented.

According to the invention this object is achieved by the features ofpatent claim 1. Advantageous developments of the invention arecharacterized in the sub-claims.

According to the invention the lid is composed of two lid members thatare captively secured to one another. The lid of the invention consistsof an inner lid member which can be screwed to the neck of the tank andis preferably provided for this purpose on a substantially cylindricalinner wall with a thread that cooperates with a corresponding externalthread of the neck of the tank, and of an outer lid member which coversthe inner lid manner approximately in the form of a bell or mushroom andcontains an upper lid wall and a circumferential wall which isintegrally connected thereto and is gripped for rotating the lid. Acoupling means is formed between the two lid members, the coupling meanscontaining a medium that below a predetermined temperature or apredetermined temperature range is of such a consistency that the mediumestablishes a non-rotational connection between the outer lid member andthe inner lid member while the medium above the predeterminedtemperature or predetermined temperature range assumes a consistency inthe case of which the outer lid member is rotatable relative to theinner lid member. This means that the medium is so hard or firm or stiffat the temperatures at which the lid can be opened without any risk offluid squirting out from the tank that the coupling means couples thetwo lid members together for joint rotation while from a predeterminedtemperature onwards the medium is so soft, flexible or even liquid thatthe inner lid member screwed onto the neck of the tank cannot be carriedalong when the outer lid member is rotated. A number of substances aresuited as the medium, for instance a low-melting metal such as a bismuthalloy, wax or plastic materials having the above-mentioned properties.

It is ensured by the configuration of the lid according to the inventionthat the container of the fluid system cannot be opened when the fluidcontained therein reaches or exceeds a predetermined temperature. Whenthe fluid has cooled down, the coupling medium solidifies such that theouter lid member can carry along the inner lid member for jointrotation.

In further details of the present invention, the outer lid member andthe inner lid member define an annular coupling chamber which is filledwith the medium. It must here be ensured through suitable sealants thatno medium can exit from the coupling chamber which is composed of wallsections rotatably arranged relative to one another. To this endinternally lubricated O-rings, for instance, may be arranged that have areduced friction coefficient and prevent the exit of the medium and theingress of air into the coupling chamber, whereby in the case of ametallic medium its oxidation is prevented.

Furthermore, projections and/or recesses are formed on the inner lidmember and the outer lid member in the area of the coupling chamber.Preferably, the wall sections of the inner lid member and the outer lidmember which define the coupling chamber are provided with attachmentsor teeth that project into the coupling chamber. Said teeth aredistributed preferably uniformly over the circumference and extendessentially over the whole height of the coupling chamber. The two rowsof teeth should here be opposite to one another such that only a smallspace remains between the free ends of the teeth. The size of theprojections or teeth, the size of the spaces, etc. must here be matchedto the strength characteristics of the medium used.

Should it become necessary to open the lid of the invention despiteexcessively high temperatures inside the tank, for instance in a garage,the lid can be cooled suddenly, for instance by cold water, so that themedium hardens in the annular coupling such that the two lid members arecoupled for joint rotation.

Further details of the invention will become apparent from the followingdescription of a preferred embodiment and from the drawing, in which:

FIG. 1 is a vertical section through an edge portion of the lidaccording to the invention, the lid being screwed to the neck of anexpansion tank; and

FIG. 2 is a horizontal section through an area of the tank neck and thelid.

The expansion tank 1 designated with reference numeral 1 on the whole,of which only a small portion is shown, contains a tank neck 2 with anexternal thread 3 that is in engagement with an internal thread 4 of aninner lid member 5. Said inner lid member 5 is captively put togetherwith a separate outer lid member 6 that covers the inner lid member 5and surrounds it on the outside in the manner of a bell or mushroom. Aclosing section which is tapered downwards in steps and which is seatedin the tank neck 2 and sealed relative thereto with three O-rings 9 iscentrally formed on the upper wall 7 of the outer lid member 6. When thelid composed of the inner lid member 5 and the outer lid member 6 isrotated into the opening position, which will be still be describedfurther below, the O-rings 9 which are seated in annular grooves 10 ofthe closing section 8 will be entrained upwards, where they lose theirsealing effect on the larger diameter areas of the tank neck.

On its edge that is the upper one in the installed position, the innerlid member 5 has an annular wall portion 11 which engages into anannular groove 12 of the outer cover member 6. The inner cover member 5is provided on its lower end portion with a horizontal wall section 13which engages into an annular groove 14 of the outer lid member 6 and isgripped from below by a nose 15 of the outer lid member, the nosedefining the annular groove 14 at the bottom, whereby the outer lidmember 6 and the inner lid member 6 are captively held together.

An annular chamber 16 which is defined on the radial inside by acircumferential wall of the inner lid member 5 and on the outside by aninner wall of the outer lid member 6 is positioned between the inner lidmember 5 and the outer lid member 6. Both walls have formed thereonteeth 17, 18 extending over the whole height of the coupling chamber 16,the teeth being evenly distributed over the circumference of the wallsand being opposite to one another so that a relatively small distanceremains between the teeth, the distance being correspondingly larger inthe area of the indentations positioned between the teeth. The annularspace 19 between the teeth and the intermediate indentations is filledwith a medium that is so hard below a predetermined temperature or apredetermined temperature range of e.g. 80° C. to 85° C. that the mediumestablishes a non-rotational connection between the outer lid member 6and the inner lid member 5 while it is so soft or liquid above saidtemperature that the outer lid member 6 is rotatable relative to theinner lid member 5.

This has the consequence that the two lid members form a non-rotationalunit below the predetermined critical temperature so that whenever theouter lid member 6 is gripped and rotated on its circumferential surface20, the inner lid member 5 is unscrewed from the tank neck 2. Within ahigher temperature range the inner lid member will not rotate when theouter lid member 6 is rotated, so that any danger caused by exitingliquid or steam is prevented in an absolutely reliable way.

The coupling chamber 16 is sealed at the top and bottom by a respectiveO-ring which is internally lubricated so that it has a low coefficientof friction.

When despite high temperatures of the tank contents the lid is to beopened e.g. by a car mechanic in a garage, this can be done by rapidlycooling the lid with cold water that is poured over the lid, whereuponthe medium in the coupling chamber will solidify right away.

1. A lid for a tank of a fluid system such as a cooling water circuit of an automotive vehicle, comprising an inner lid member which can be screwed to the neck of the tank, and an outer lid member which covers the inner lid member in the manner of a bell or mushroom, and a coupling means is formed between the lid member and the outer lid member, the coupling means containing a medium which below a predetermined temperature or a predetermined temperature range shows such a consistency that the medium establishes a non-rotational connection between the outer lid member and the inner lid member while the medium above the predetermined temperature or the predetermined temperature range assumes such a consistency that the outer lid member is rotatable relative to the inner lid member.
 2. The lid according to claim 1, wherein the outer lid member is provided with an internal thread which can be screwed to an external thread of the neck of the tank.
 3. The lid according to claim 1, wherein the outer lid member and the inner lid member define thereinbetween an annular coupling chamber which is filled with the medium.
 4. The lid according to claim 1 wherein projections and/or recesses are formed on the inner lid member and the outer lid member in the area of the coupling chamber.
 5. The lid according to claim 1 wherein the inner lid member and the outer lid member are provided with teeth projecting into the coupling chamber. 